This invention relates to an electron-device housing or package with a pulse transformer, and more particularly to such a package having a laser diode.
There are many applications where it is desired to use a driver circuit with a bipolar or field-effect transistor output stage to drive a high power pulsed semiconductor laser diode. Laser diodes typically operate with an electrical pulse of 4 volts potential, 40 amperes or more current, 50 nanoseconds duration, and a repetition rate of 200,000 pulses per second. The best conventional packages heretofore have had approximately 10 nanohenries inductance in series with 40 milliohms resistance. Therefore 30 volts must be applied to obtain the desired maximum rise time of 20 nanoseconds, neglecting the effects of the lead from the driver to the laser package. High voltage thyristor output stages can be used to drive laser diodes in the conventional packages since they can overcome the inductance with higher voltages. Unfortunately, high pulse repetition rates cannot be achieved with a thyristor output stage.
Examples of laser diode mounting structures and packages include Hacskaylo U.S. Pat. No. 3,946,416, in which inductive reactance and capacitive reactance are balanced to leave only pure resistance in the input to the diode, and one side of the diode is mounted on a heat sink that is electrically connected to the housing. Jennings U.S. Pat. No. 4,161,747 shows a diode laser mounted within a helium refrigerator using a braided copper ground strap for shock isolation while providing a good thermal link to the cold tip. Allen, Jr. et al U.S. Pat. No. 4,315,225 shows an array structure in which each diode is soldered between metal plates for intimate thermal and electrical contact, with an insulated spacer between the plates, to form a sandwich package; and several of them are stacked and driven in series.
Therefore there has been needed a package which efficiently couples a laser diode to a transmission line having greatly differing characteristic impedance while still providing sufficient heat sinking that the laser diode can be operated at high current levels and high repetition rates.
My copending application Ser. No. 277,074 discloses a package for matching the characteristic impedance of a transmission line to the impedance of a pulsed semiconductor laser diode so that short duration pulses of light can be produced with a fast repetition rate. The package mounts the laser diode on the center post of a one turn secondary or a toroidal transformer whose multiturn primary is connected to the transmission line. The center also provides heat sinking for the diode. The package provides very good performance with a fast rise time and low drive voltage, and has several advantages over the prior art. However, the package was difficult to fabricate, and once made it was difficult to replace a burned out diode.